The invention relates to a method for automatic allocation of a motor sensor to a power section in an electrical drive system; and also to an electrical drive system which utilizes the aforesaid method.
In industrial automation machines having electrical drives, and particularly where a number of electrical drives are combined, such as in numerically controlled machine tools and robots, one problem which arises frequently is the proper allocation of motor sensors connected to the power section. This is particularly so where a number of electrical drives have associated sensor systems, because there is a considerable risk of an incorrect association of a sensor to the power section due to a false connection, etc. Faulty connections can result in hazards, for example for the operator of a robot.
FIG. 5 shows a conventional drive system with three motors M1 to M3, which are fed via respective power cables LK1 to LK3 from respectively associated power sections L1 to L3. Each motor M1, M2, M3 has an associated motor sensor G1, G2 and G3, which is connected via a respective sensor cable GK1 to GK3 to the associated power section L1 to L3. This results in the formation of a control loop for controlling each motor M1 to M3. Thus, normally, in addition to the power connection LK1 to LK3, a power section L1 to L3 also has a connection GK1 to GK3 for the motor sensor G1 to G3. Each motor sensor G1 to G3 must be connected correctly to the associated sensor interface GK1 to GK3, and no other association is possible for technically correct operation. If, for example in the case of two shafts, the motor sensor connections GK1, GK2, GK3 are interchanged, this fault cannot be detected without activating the motors M1 to M3 which can result in a considerable hazard potential for an operator of such a machine.
The object of the present invention is to provide a capability for automatic allocation between a power section and the motor sensor connected to this power section by which even flexible connection variants such as those shown in FIG. 6 and FIG. 7 are possible. The arrangement in FIGS. 6 and 7 have the basic design shown in FIG. 5. However, FIG. 6 incorporates a central control unit R, for the evaluation of all the motor sensors G1 to G3 which drive all three power sections L1 to L3. Accordingly, all the sensor interfaces GK1 to GK3 are also connected to the control unit R.
FIG. 7 shows the cascading of motor sensors MG1 to MG3. In this case, the control unit R as shown in FIG. 6 is again provided, but without dedicated sensor cables GK1 to GK3 routed separately from each motor sensor MG1 to MG3 to the control unit R. Instead, and a communication interface is provided. The motor sensors G1 to G3 are networked to one another via this communication interface, for example using line topology, via a bus system or by point-to-point links. Only the first motor sensor G1 in the line is connected to the control unit R. Further, motor sensors G2, G3 are connected by means of a serial link to the respectively preceding motor sensor, i.e., G2 to G1, and G3 to G2, etc., in a cascade.
Conventionally, the process of allocating a power section and the associated motor sensor can be carried out only via a configuration process for these elements. This however, involves an additional action by the person setting up the system as shown in FIG. 5. Furthermore, errors can occur during the allocation process which are not readily apparent.
Also, new sensor interfaces are increasingly being introduced with modem drive systems, which allow the configurations shown in FIGS. 6 and 7. Accordingly, the present invention also has as an objective to provide a simple procedure for setting-up such configurations.
The present invention, achieves the aforesaid objective by a method for automatic allocation of a motor sensor to a power section within an electrical drive system. Specifically, a closed loop is formed from a control unit, the power section, a motor and the motor sensor. The control unit transmits a preset feature signature via the power section, which feature is passed back again to the control unit via the closed loop. The control unit compares a control loop structure with the actual wiring of the motor sensor and power section.
It has been found to be particularly advantageous if a pulse, in particular a preset voltage pulse, which can be uniquely identified is provided as the feature. Nevertheless, as an alternative, a unique characteristic value can also be preset. The method according to the present invention is particularly effective where an identical pulse or signature feature is emitted simultaneously via the power section on all the phases of the motor. This provides a very effective comparison of the control loop structure with the actual wiring, with the control unit evaluating the motor sensor to determine whether the pulse has occurred.
Alternatively, the object of the present invention can also be achieved by a method for automatic allocation of a motor sensor to a power section within an electrical drive system, wherein a closed loop is formed from a control unit, the power section, a motor and the motor sensor. The control unit transmits the feature via the motor sensor, which feature is passed back again to the control unit via the closed loop, and the control unit compares the control loop structure with the actual wiring. In this case, it has also been found to be particularly advantageous for a pulse, in particular a voltage pulse which can be uniquely identified, to be preset as the transmitted feature. However, a unique characteristic value can also be used as the preset feature. The aforesaid communication direction enables a simple technical transmission via an existing power line to be used as an alternative to costly additional lines, provided that the motor and the power section are connected via a power line onto which the feature may be, or is modulated for transmission.
Frequently, safe electrical isolation in a drive system is required for compliance with safety directives and standards. While this makes it more difficult to produce a closed loop between the components described above, couplings by means of parasitic capacitances may be used to satisfy the safe electrical isolation requirements within the closed loop.
While the aforesaid communication direction is from the power section to the motor, it has been found to be advantageous to use a temperature sensor to effect the safe electrical isolation between the motor and the motor sensor. The temperature sensor is arranged in the motor winding and is evaluated by the control unit via the motor sensor for coupling of a pulse caused by a parasitic capacitance.
In the case of communication in the opposite direction, a temperature sensor can also be used to effect safe electrical isolation between the motor and the motor sensor. Here, the temperature sensor is arranged in the motor winding and the temperature sensor is evaluated by the control unit via the coupled motor and the power section, with a pulse caused by a parasitic capacitance.
Alternatively, the problem of safe electrical isolation can be accomplished if the motor is connected via a power line to the power section, with the motor sensor being supplied with voltage via the power section. The lines for supplying voltage to the motor sensor are also arranged in the power line. Couplings by means of parasitic capacitances are used between the lines for supplying voltage to the motor and the lines for supplying voltage to the motor sensor within the power line to overcome safe electrical isolation between the motor and the motor sensor.
The object of the present invention, as described above, is also achieved by an electrical drive system, having a motor, a power section, a control unit and a motor sensor, which are connected to one another such that they form a closed loop, in which a feature is transmitted by the control unit. This feature can be transmitted in one direction of the closed loop and can be detected from the other direction so that a control loop structure of the drive system can be compared with the actual wiring. Significant advantages can be achieved by this arrangement of a drive system when operated using the method according to the invention described above.